FEET WITH ENTIRE WEBS. 291 



being the most webbed, are the most aquatic, or the 

 best swimming feet of the whole. But such is not 

 the case in fact; and when we come to consider the 

 matter a httle more closely, we find that such ought 

 not to be the case, according to the structural analogy. 

 The back toe of a bird, whether its path be upon the 

 land or the water, is never an auxiliary to the foot in 

 merely progressive motion; it is always rather the 

 reverse, and placed there in accordance with some- 

 thing else ; and thus the produced hind toe, which is 

 rudimental or wanting in all birds which have their 

 motion confined either to the surface of the earth or 

 to the water, indicates an aerial character in this 

 group. Accordingly, the pelicans, cormorants, darters, 

 and several others which have feet of this description^ 

 often migrate inland, and perch and also build in trees ; 

 and even those which never or rarely quit the sea, 

 build high upon the cliffs, and take their repose upon 

 the land, while some of the swimmers fold their head 

 under their wing and sleep in safety upon the water. 



These birds have the feet differently articulated in 

 the different genera ; as, for instance, the cormorant 

 has them much farther back than the gannet, and is 

 not able to carry the axis of its body in so horizontal 

 a position. But they all " stand well " on their legs, 

 only the feet, in consequence of that form which is 

 required to answer the habit of the bird in feeding, 

 come rather into contact with each other, and render 

 the walk awkward and swinging. The tarsi are per- 

 pendicular, or nearly so'; but they are thrown wide of 

 each other by the' position of the tibiae ; and it is to 

 this wide setting of the tarsi, and not to any want of 

 firmness in the articulation of the toes, that the birds 

 owe their rolling gait when they walk. The foot is 

 nearly a semicircle, or rather a semioctagon of un- 

 u 2 



